In this Aug. 14, 2012 file photo, President Obama is greeted on stage by a thumbs-up from Mike Dufel of Cedar Falls, Iowa, during a campaign event at Waterloo Center for the Arts in Waterloo, Iowa. (AP Photo/Carolyn Kaster, File) less

In this Aug. 14, 2012 file photo, President Obama is greeted on stage by a thumbs-up from Mike Dufel of Cedar Falls, Iowa, during a campaign event at Waterloo Center for the Arts in Waterloo, Iowa. (AP ... more

In this Oct. 16, 2012 file photo, Republican presidential candidate, former Massachusetts Gov. Mitt Romney and President Barack Obama spar during the second presidential debate at Hofstra University in Hempstead, N.Y. (AP Photo/Charlie Neibergall, File) less

In this Oct. 16, 2012 file photo, Republican presidential candidate, former Massachusetts Gov. Mitt Romney and President Barack Obama spar during the second presidential debate at Hofstra University in ... more

In this April 27, 2012 file photo, President Obama and first lady Michelle Obama are saluted by soldiers as they arrive at the Fort Stewart Army post in Fort Stewart, Ga. (AP Photo/David Goldman, File)

In this April 27, 2012 file photo, President Obama and first lady Michelle Obama are saluted by soldiers as they arrive at the Fort Stewart Army post in Fort Stewart, Ga. (AP Photo/David Goldman, File)

Photo: David Goldman, Associated Press

In this April 27, 2012 file photo, President Obama and first lady... Photo-3695619.51928 - SFGate

In this July 23, 2012 file photo, President Obama gestures at a campaign stop in Oakland, Calif. (AP Photo/Paul Sakuma, File)

In this July 23, 2012 file photo, President Obama gestures at a campaign stop in Oakland, Calif. (AP Photo/Paul Sakuma, File)

Photo: Paul Sakuma, Associated Press

In this July 23, 2012 file photo, President Obama gestures at a... Photo-3695610.51928 - SFGate

Image 18 of 37

In this March 1, 2012 file photo, President Obama waves to the crowd as he walks through a snowstorm after getting off Air Force One in Manchester, N.H. (AP Photo/Winslow Townson, File)

In this March 1, 2012 file photo, President Obama waves to the crowd as he walks through a snowstorm after getting off Air Force One in Manchester, N.H. (AP Photo/Winslow Townson, File)

Photo: Winslow Townson, Associated Press

In this March 1, 2012 file photo, President Obama waves to the... Photo-3695607.51928 - SFGate

Image 19 of 37

In this Feb. 16, 2012 file photo, Mitt Romney is reflected in a window as he talks with deputy campaign manager Katie Gage on his campaign bus between Monroe, Mich., and Farmington Hills, Mich. (AP Photo/Gerald Herbert, File) less

In this Feb. 16, 2012 file photo, Mitt Romney is reflected in a window as he talks with deputy campaign manager Katie Gage on his campaign bus between Monroe, Mich., and Farmington Hills, Mich. (AP Photo/Gerald ... more

In this July 14, 2012 file photo, President Obama holds a campaign... Photo-3695593.51928 - SFGate

Image 29 of 37

In this April 23, 2012 file photo, President Obama strikes the Heisman pose after he awarded the Commander-in-Chief Trophy to the Air Force Academy football team in the East Room of the White House in Washington. (AP Photo/Charles Dharapak, File) less

In this April 23, 2012 file photo, President Obama strikes the Heisman pose after he awarded the Commander-in-Chief Trophy to the Air Force Academy football team in the East Room of the White House in ... more